[bananas] Second and Third patches for 15OCT98

[Pat Murphy]

Here are the second and third patches for 15OCT98:

   Task     Description of problem                             Date
   -------------------------------------------------------------------
   Many     Gridded Clean Component subtraction in error     1999-01-05
   FITLD    Init error when appending to >2 Gbyte files      1999-01-19

Complete information on these, including links to the modified source code
and instructions for rebuilding the affected tasks, can be obtained via:

	 http://www.cv.nrao.edu/aips/15OCT98/patches.html

The text of the equivalent README.15OCT98 patch file is also appended
here. 

  ----------------------------------------------------------------------

ID:           2.
Task:         Gridded Clean-component modeling

Summary:      A bug has been found in the code which subtracts a Clean
              Component model from uv data using the gridded method.
              The term which specifies the Z separation of a field
              from the phase center (sqrt (1 - xshift**2 - yshift**2))
              was supposed to be scaled by the ratio of the frequency
              of the first spectral (or IF) channel in the model
              subtraction to the reference frequency.  This scaling
              factor was omitted from the code, apparently forever or
              at least since 1990.  The bug can be important. In a
              test case, with data at declination -26, a strong
              interfering source 1 degree north of the phase center,
              and a frequency difference of 20%, the Clean in IMAGR
              was quickly divergent. Note that this test involves a
              large frequency difference, a largish separation, and a
              declination and direction of separation that emphasize
              the W * Z term.  

	      There was no error when the frequency of the first
              channel/IF was the reference frequency.  This is usually the
              case in multi-IF bandwidth synthesis with BIF = 1.  In
              spectral-line, single-channel synthesis the frequency
              differences are normally very small.  And, at more northerly
              declinations or field separations with horizontal parts of
              the vector, the W * Z term is less important.  Perhaps this
              is why this error was not reported and found until now.


Files:        /15OCT98/Q/SUB/NOTST/ALGSUB.FOR
              /15OCT98/Q/SUB/NOTST/ALGSTB.FOR

Fix:          1. Fetch the files listed above and place them in
                 the corresponding area ($QNOT) on your system.
              2. COMRPL $QNOT/ALGSUB $QNOT/ALGSTB
              3. COMLNK $QPGOOP/{BLING,GPHAS,IMAGR,SCMAP,WFCLN}
                 COMLNK $QYPGNOT/MX
                 COMLNK $QPGNOT/{BLCAL,BPASS,CALIB,CPASS}
                 COMLNK $QPGNOT/{FRING,KRING,LPCAL,PCAL}
                 COMLNK $QPGNOT/{UVADC,UVSUB}

Documentor:   Eric W Greisen
Date:         1999-01-05

  ----------------------------------------------------------------------

ID:           3. Appending to very large files
Task:         FITLD

Summary:      A bug in the routine that initializes uv data I/O was
              found when it attempts to append to a file that is already
              larger than 2 Gigabytes.  This only applies on HPs, DECs,
              and those Solaris 2.6+ systems compiled to allow such large
              files.  UVINIT is used everywhere, but FITLD is the main
              place that this problem would be seen.

Files:        /15OCT98/APL/SUB/UVINIT.FOR

Fix:          1. Fetch the file listed above and place it in the
                 corresponding area ($APLSUB) on your system.
              2. COMRPL $APLSUB/UVINIT
              3. COMLNK $APGNOT/FITLD

Documentor:  Eric W. Greisen
Date:        1999-01-19

  ----------------------------------------------------------------------

-- 
  \|/  ____  \|/   Pat Murphy; email http://orangutan.cv.nrao.edu/kippure.html
   @~ / oO \ ~@                  Division Head, NRAO/Charlottesville Computing
   /_( \__/ )_\       Plan, PGP, Pages: http://orangutan.cv.nrao.edu/plan.html
      \_U__/                               "The truth points to itself" - Kosh